Drill collars are robust components positioned above a drill bit proximate the lower end portion of a drill string. The stress and vibration that the drill collar is designed to endure are oftentimes transmitted to the “standard” pipes that are positioned above the drill collar. Standard drill pipes, however, are not designed to withstand such stress and vibration. Accordingly, heavy weight drill pipes (“HWDPs”) are often used to provide a buffer or transition between the drill collar and standard drill pipes.
HWDPs include at least one joint coupled to a pipe. One conventional method for coupling the joint and the pipe includes friction welding. Before welding, the weld area of the joint is preheated to between about 177° C. and about 427° C., for example, by an induction heater. During the friction welding process, the joint is rotated about its longitudinal axis while the pipe remains stationary. An end portion of the rotating joint is then placed in contact with an end portion of the stationary pipe, and the friction between the joint and the pipe generates heat in excess of about 1040° C. The heat and force enable the joint and the pipe to fuse together at a weld zone/region. Once the joint and the pipe begin to fuse or weld together, the rotating joint is rapidly decelerated to a stationary position, and the weld region between the joint and the pipe is allowed to gradually cool due to the temperature differential between the weld region and the surrounding environment.
After the weld region cools, it is tempered (i.e., re-heated) at between about 500° C. and about 730° C., for example, by the induction heater. The weld region is allowed to gradually cool again due to the temperature differential between the weld region and the surrounding environment. This process is called stress relief treatment.
Alternatively, the weld region may experience quenching and tempering treatment. After the weld region cools, it is re-heated to between about 780° C. and about 1000° C., for example, by the induction heater. The weld region is then quenched with pressurized air, water, brine, oil, or the like for rapid cooling. This step is oftentimes referred to as “active quenching” or “forced quenching.” Once the weld region cools, it is tempered at between about 500° C. and about 730° C., for example, by the induction heater. Finally, the weld region is allowed to gradually cool due to the temperature differential between the weld region and the surrounding environment.